For some, too much sunshine may bring on the blues

Those hit by depression in warmer weather complain of insomnia, anxiety, appetite loss.

Take 30-year-old Saskia Smith, an illustrator who works part time in the billing department of a legal firm. She spent most of last summer's dog days prone in bed with the velvet drapes in her Mid-City apartment pulled tightly shut.

"Other times of year, I'm basically an upbeat person," Smith says. "But when summer hits, it's like I'm operating on a low battery. Last summer, I had no desire to eat, I lost 15 pounds, I had anxiety attacks and I stopped seeing any of my friends. Even going to the grocery store felt like an impossible task."

Smith, who grew up in Seattle and has lived in New York City and Germany (all areas with notably moody skies), is convinced she has seasonal affective disorder, or SAD. The condition first surfaced after she and her husband moved to Los Angeles almost three years ago. "It's the unrelenting sun day after day after day," she says. "I feel like I'm trapped and there's no relief from it. At my lowest point [last summer] I just wanted to die."

Although most people consider seasonal affective disorder to be a winter ailment brought on by waning sunlight, Smith and others say there's a summer version -- and it packs a wallop as well.

Researchers estimate that about 1% of the population suffer from summer depression, compared with 5% for the winter variety. Although summer depression has been mentioned in ancient writings, as well as in scientific journals sporadically for the last 20 years, the relatively low prevalence in the U.S. has meant it hasn't gotten much serious consideration, says Dr. Thomas Wehr, a Bethesda, Md., psychiatrist and former National Institutes of Mental Health researcher.

"The closer you get to the equator -- countries like India, China and Brazil -- it turns out the condition is quite common. But here a lot of people with summer depression feel isolated," says Wehr, an expert on seasonal affective disorder.

Role of the thyroid

Wehr and NIMH colleagues first became aware of summer SAD when they were studying winter depression in the 1980s. "In the course of our research, we'd regularly get letters from people saying winter depression was interesting but they seemed to have the opposite problem. However, the symptoms were different."

People with winter depression tend to sleep more, have less energy, gain weight and have carbohydrate cravings. Summer depressives tend to be plagued with decreased sleep, weight loss and anxiety.

Researchers say that some people may be especially sensitive to heat, which could influence their production of various hormones. "We know thyroid hormone is suppressed by heat and growth hormone and prolactin are stimulated by heat," Wehr says.

Lack of thyroid hormone can cause energy drain, and too much growth hormone and prolactin can lead to lethargy and lack of libido. In addition, prolactin is known to repress the effects of dopamine, a brain chemical linked to feelings of enjoyment and pleasure. Light on the skin can also influence the production of hormones, but preliminary NIMH research points to heat more than light as the culprit in summer depression.

Typical to depression in general, researchers say, more women than men appear to suffer from summer SAD. The condition generally crops up in childbearing years and studies point to a genetic link; more than two-thirds of SAD patients have a first-degree relative with a mood disorder.

"The problem is that right now we just don't know enough about summer depression to say it gives us prognosis and treatment," says Dr. Daniel F. Kripke, professor of psychiatry at UC San Diego. "Until we do, it's not very useful."

Winter blues responds well to light therapy, and because researchers think the summer version is a condition of heat, reducing heat should work as a treatment for summer depressives.

That doesn't seem to be the case. A pilot study by Wehr and colleagues at NIMH found that manipulating temperature for a period of time was salutary but didn't have lasting effects on summer SAD patients.

"In our study, people would improve [with cooling] and then very quickly the symptoms would come back," Wehr says.

Antidepressants help

Some researchers take issue with associating winter depression with summer depression or labeling it "reverse SAD."

"Calling it 'reverse SAD' only confuses the issue," says Michael Terman, director of the Center for Light Treatment and Biological Rhythms at New York-Presbyterian Hospital. "It is not a light-related phenomenon and should not be considered the flip side of winter depression." Standard antidepressants are the only medical intervention that's been shown to be effective, he says.

Wehr agrees medication tends to work, but says the drugs may vary. "Some respond to Prozac-like drugs, some people respond to Wellbutrin. I've even had people respond to lithium and only lithium. They only take it during the summer," Wehr says.